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Thursday, June 14, 2012

"Tropical" Methane Lake Found on Titan

An oasis of liquid methane has unexpectedly been discovered amid the tropical dunes of Saturn's moon Titan, researchers say.

This lake in the otherwise dry tropics of Titan hints that subterranean channels of liquid methane might feed it from below, scientists added.

Titan has clouds, rain and lakes, like Earth, but these are composed of methane rather than water. However, methane lakes were seen only at Titan's poles until now — its tropics around the equator were apparently home to dune fields instead.

Now near-infrared pictures of Titan from the Cassini spacecraft currently orbiting Saturn collected since 2004 suggest a vast methane lake exists on the surface in the moon's tropics, one about 925 square miles (2,400 square kilometers) large and at least three feet (1 meter) deep.

"Titan's tropical lake is roughly the size of the Great Salt Lake in Utah during its lowest recorded level," study lead author Caitlin Griffith, a planetary scientist at the University of Arizona at Tucson, told SPACE.com. "Our work also suggests the existence of a handful of smaller and shallower ponds similar to marshes on Earth with knee- to ankle-level depths."

A number of models of methane's behavior on Titan convincingly show that lakes are not stable at the moon's tropical latitudes. "Any liquid deposited in the tropical surface evaporates quickly and eventually is transported by Titan's circulation to the poles, where the large polar lakes appear," Griffith said.

"This discovery was absolutely not expected," Griffith said. "Lakes at the poles are easy to explain, but lakes in the tropics are not."